According to Vermeij and Synder (2018: p. 61)) and WoRMS (2023), the extant (living) marine gastropod Cyrtulus undatus (Gmelin, 1791) is now classified in the family Fasciolariidae, a very diverse group (approx.. 500 spp., made up of such shells commonly known as the “spindles,” “tulip shells,” “horse conchs,” etc. Fasiolariids are predatory neogastropods. Many of the fasciolariid genera have complex taxonomic histories that have recently and are continuing to be much better understood via the use DNA molecular studies, in combination with other anatomical features (radular teeth, etc.) (Couto, 2016). Scientific literature published even 10 years ago on fasciolariid identification/classification is now very out-of-date, with on-going studies that will undoubtedly produce new findings.
Cyrtulus undatus, which used to be classified in family Fusinidae and in genus Fusinus, has a shell that can be up to 25.3 cm long. Its shell has a fusiform shape, with rounded knobs and low spiral ribs. The shell color is white, but the periostratum, a protective outer layer during life, is brown.
This species is benthic (lives on the ocean floor) in tropical waters, mainly in the southwest Pacific (southern Japan, Malaysia, and northern Australia). It occurs also in Hawaii, where it has been identified as Fusinus sandvicensis (Sowerby, 1880), according to Kay (1979, p. 278) and found via dredge hauls at depths of from 50 to 150 m. It is a “non-broadcast spawner,” that is to say that its life cycle does not include a trochophore stage.
The common name of this shell is the “wavy spindle shell” and also “Legrand’s wavy spindle.” The “wavy” designation is apparently because the tip of spire, as well as the long anterior canal, can be slightly curved (or “wavy), like the shell illustrated below.
Three views (apertural, abapertural, and right side) of the fasciolariid gastropod Cyrtulus undatus (Gmelin, 1791), height 19 cm, width 6 cm [side width 5.3 cm], Philippines.
References Cited:
Couto, D.R. de. 2016. A phylogenetic analysis of Fasciolariidae (Gastropoda: Buccinoidea). 273 pp. Dissertation, Museu da Universidade de Sa Paulo, Brazil. Available as a free pdf. (internet download.)
Kay, E. A. 1979. Hawaiian marine shells. Reef and Shore Fauna of Hawaii: Section 4. Mollusca. 653 pp.
Vermeij, G.J. and M.A. Synder. 2018. Proposed genus-level classification of large species of Fusininae (Gastropoda, Fasiolariidae). Basteria 82(4-6), pp. 57-82.
WoRMS, 2023. http://marinespecies.org
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